Cooling system

ABSTRACT

A cooling system that cools a heat generating source mounted on a vehicle includes: a compressor that circulates refrigerant; a first heat exchanger that performs heat exchange between the refrigerant and outside air; a decompressor that decompresses the refrigerant; a second heat exchanger that performs heat exchange between the refrigerant and air-conditioning air; and a cooling device that is provided on a path of the refrigerant flowing between the first heat exchanger and the decompressor and that uses the refrigerant to cool the heat generating source. A capillarity generating portion that causes the refrigerant to rise due to capillarity is provided inside the cooling device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a cooling system and, more particularly, to acooling system that utilizes a vapor compression refrigeration cycle tocool a heat generating source mounted on a vehicle.

2. Description of Related Art

In recent years, hybrid vehicles, fuel cell vehicles, electric vehicles,and the like, that run using driving force of a motor become a focus ofattention as one of measures against environmental issues. In suchvehicles, electrical devices, such as a motor, a generator, an inverter,a converter and a battery, exchange electric power to generate heat.Therefore, these electrical devices need to be cooled. Then, there hasbeen suggested a technique that utilizes a vapor compressionrefrigeration cycle, which is used as a vehicle air conditioner, to coola heat generating element.

For example, Japanese Patent Application Publication. No. 2006-290254(JP 2006-290254 A) describes a cooling system for a hybrid vehicle. Thecooling system includes: a compressor that is able to introduce andcompress gaseous refrigerant; a main condenser that is able to coolhigh-pressure gaseous refrigerant using ambient air to condense thehigh-pressure gaseous refrigerant; an evaporator that is able toevaporate low-temperature liquid refrigerant to cool an refrigeratingobject; and a decompressing unit, and a heat exchanger, which is able toabsorb heat from a motor, and a second decompressing unit are connectedin parallel with the decompressing unit and the evaporator.

Japanese Patent Application Publication No. 2007-69733 (JP 2007-69733 A)describes a system in which a heat exchanger that exchanges heat withair-conditioning air and a heat exchanger that exchanges heat with aheat generating element are arranged in parallel with each other in arefrigerant line routed from an expansion valve to a compressor andrefrigerant for an air conditioner is utilized to cool the heatgenerating element. Japanese Patent Application Publication No.2001-309506 (JP 2001-309506 A) describes a cooling system thatcirculates refrigerant of a vehicle air-conditioning refrigeration cyclethrough a cooling member of an inverter circuit portion that executesdrive control over a vehicle drive motor and, when coolingair-conditioning air stream is not required, cooling of air-conditioningair stream by an evaporator of the vehicle air-conditioningrefrigeration cycle is suppressed.

On the other hand, as for the internal structure of a cooling systemfor, flowing refrigerant, Japanese Patent Application Publication No.2008-218718 (JP 2008-218718 A) describes a structure that a space insidea casing is partitioned by wall surfaces to form a plurality ofaccommodating portions and then coolant is accommodated in theaccommodating portions to thereby keep coolant inside the accommodatingportions even when the liquid surface of coolant is inclined withrespect to the lower face of the casing. Japanese Patent ApplicationPublication No. 2010-107153 (JP 2010-107153 A) describes an evaporator.The evaporator includes a refrigerant supply unit that storesrefrigerant liquid flowing thereinto from a liquid tube and thatsupplies the refrigerant liquid and a wick that transfers refrigerantliquid by capillary force.

In cooling a heat generating source mounted on a vehicle, refrigerantliquid may be caused to flow through a cooling portion for cooling theheat generating source to cool the heat generating source through heatexchange between refrigerant and the heat generating source. While thevehicle is running on a hill, the position of the vehicle inclines and,accordingly, the position of the cooling portion inclines. Thus, theliquid surface of refrigerant liquid inside the cooling portion inclinesrelatively with respect to the cooling portion. There are concerns abouta reduction in driving force for flowing refrigerant liquid inside thecooling portion depending on the position of the cooling portion. Inthis case, there is an inconvenience that refrigerant liquid does notreach all the areas in the direction in which refrigerant liquid flowsinside the cooling portion and, as a result, cooling of the heatgenerating source is insufficient.

SUMMARY OF THE INVENTION

The invention provides a cooling system that is able to reliably cool aheat generating source irrespective of the position of a vehicle.

An aspect of the invention relates to a cooling system that cools a heatgenerating source. The cooling system includes: a compressor thatcirculates refrigerant; a first heat exchanger that performs heatexchange between the refrigerant and outside air; a decompressor thatdecompresses the refrigerant; a second heat exchanger that performs heatexchange between the refrigerant and air-conditioning air; and a coolingdevice that is provided on a path of the refrigerant flowing between thefirst heat exchanger and the decompressor and that uses the refrigerantto cool the heat generating source. A capillarity generating portionthat causes the refrigerant to rise due to capillarity is providedinside the cooling device.

In the above cooling system, the capillarity generating portion may beformed by subjecting an inner face of a bottom portion of the coolingdevice to surface processing.

In the above cooling system, the capillarity generating portion mayextend in a flow direction of the refrigerant flowing through thecooling device.

In the above cooling system, the heat generating source may be inthermal contact with an outer face of a bottom portion of the coolingdevice. The above cooling system may further include: a first linethrough which the refrigerant flows between the compressor and the firstheat exchanger; a second line through which the refrigerant flowsbetween the cooling device and the decompressor; and a communicationline that provides fluid communication between the first line and thesecond line.

With the cooling system according to the aspect of the invention, it ispossible to reliably cool a heat generating source mounted on a vehicleirrespective of the position of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the invention will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a schematic view that shows the configuration of a coolingsystem according to an embodiment;

FIG. 2 is a Mollier chart that shows the state of refrigerant in a vaporcompression refrigeration cycle;

FIG. 3 is a schematic view that shows the flow of refrigerant that coolsan HV device during operation of the vapor compression refrigerationcycle;

FIG. 4 is a schematic view that shows the flow of refrigerant that coolsthe HV device during a stop of the vapor compression refrigerationcycle;

FIG. 5 is a partially cross-sectional view of a cooling device;

FIG. 6 is a partially enlarged perspective view of the inner face of thebottom portion of a cooling passage;

FIG. 7 is a schematic view that shows a vehicle that is running on aflat road;

FIG. 8 is a cross-sectional view that shows the state of refrigerantliquid inside the cooling passage while the vehicle is running on theflat road;

FIG. 9 is a schematic view that shows the vehicle that is running on anuphill;

FIG. 10 is a cross-sectional view that shows the state of refrigerantliquid inside the cooling passage while the vehicle is running on theuphill;

FIG. 11 is a schematic view that shows the vehicle that is running on adownhill; and

FIG. 12 is a cross-sectional view that shows the state of refrigerantliquid inside the cooling passage while the vehicle is running on thedownhill.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the invention will be described withreference to the accompanying drawings. Note that, in the followingdrawings, like reference numerals denote the same or correspondingportions and the description thereof is not repeated.

FIG. 1 is a schematic view that shows the configuration of a coolingsystem 1 according to the present embodiment. As shown in FIG. 1, thecooling system 1 includes a vapor compression refrigeration cycle 10.The vapor compression refrigeration cycle 10 is, for example, mounted ona vehicle in order to cool the cabin of the vehicle. Cooling using thevapor compression refrigeration cycle 10 is performed, for example, whena switch for cooling is turned on or when an automatic control mode inwhich the temperature in the cabin of the vehicle is automaticallyadjusted to a set temperature is selected and the temperature in thecabin is higher than the set temperature.

The vapor compression refrigeration cycle 10 includes a compressor 12, aheat exchanger 14 that serves as a first heat exchanger, a heatexchanger 15, an expansion valve 16 that is an example of adecompressor, and a heat exchanger 18 that serves as a second heatexchanger. The vapor compression refrigeration cycle 10 further includesa gas-liquid separator 40. The gas-liquid separator 40 is arranged on apath of refrigerant between the heat exchanger 14 and the heat exchanger15.

The compressor 12 is actuated by a motor or engine equipped for thevehicle as a power source, and adiabatically compresses refrigerant gasto obtain superheated refrigerant gas. The compressor 12 introduces andcompresses gaseous refrigerant flowing from the heat exchanger 18 duringoperation of the vapor compression refrigeration cycle 10, anddischarges high-temperature and high-pressure gaseous refrigerant to arefrigerant line 21. The compressor 12 discharges refrigerant to therefrigerant line 21 to thereby circulate refrigerant in the vaporcompression refrigeration cycle 10.

The heat exchangers 14 and 15 cause superheated refrigerant gas,compressed in the compressor 12, to release heat to an external mediumwith a constant pressure and to become refrigerant liquid. High-pressuregaseous refrigerant discharged from the compressor 12 releases heat tothe surroundings to be cooled in the heat exchangers 14 and 15 tothereby condense (liquefy). Each of the heat exchangers 14 and 15includes tubes and fins. The tubes flow refrigerant. The fins are usedto exchange heat between refrigerant flowing through the tubes and airaround the heat exchanger 14 or 15. Each of the heat exchangers 14 and15 exchanges heat between refrigerant and natural draft generated as thevehicle runs or cooling air supplied by forced draft from a cooling fan,such as an engine cooling radiator fan. Due to heat exchange in the heatexchangers 14 and 15, the temperature of refrigerant decreases, andrefrigerant liquefies.

The expansion valve 16 causes high-pressure liquid refrigerant, flowingthrough a refrigerant line 25, to be sprayed through a small hole toexpand into low-temperature and low-pressure atomized refrigerant. Theexpansion valve 16 decompresses refrigerant liquid, condensed in theheat exchangers 14 and 15, into wet steam in a gas-liquid mixing state.Note that a decompressor for decompressing refrigerant liquid is notlimited to the expansion valve 16 that performs throttle expansion;instead, the decompressor may be a capillary tube.

Atomized refrigerant flowing inside the heat exchanger 18 vaporizes toabsorb heat of ambient air that is introduced so as to contact with theheat exchanger 18. The heat exchanger 18 uses low-temperature andlow-pressure refrigerant decompressed by the expansion valve 16 toabsorb heat of vaporization, required at the time when wet steam ofrefrigerant evaporates into refrigerant gas, from air-conditioning airflowing to the cabin of the vehicle to thereby cool the cabin of thevehicle. Air-conditioning air of which heat is absorbed by the heatexchanger 18 to decrease its temperature flows into the cabin of thevehicle to cool the cabin of the vehicle. Refrigerant absorbs heat fromthe surroundings in the heat exchanger 18 to be heated.

The heat exchanger 18 includes tubes and fins. The tubes flowrefrigerant. The fins are used to exchange heat between refrigerantflowing through the tubes and air around the heat exchanger 18.Refrigerant in a wet steam state flows through the tubes. Whenrefrigerant flows through the tubes, the refrigerant absorbs heat of airin the cabin of the vehicle as latent heat of vaporization via the finsto evaporate, and further becomes superheated steam because of sensibleheat. Vaporized refrigerant flows into the compressor 12 via arefrigerant line 27. The compressor 12 compresses refrigerant flowingfrom the heat exchanger 18.

The vapor compression refrigeration cycle 10 further includes therefrigerant line 21, refrigerant lines 22, 23 and 24, the refrigerantline 25, a refrigerant line 26 and the refrigerant line 27. Therefrigerant line 21 provides fluid communication between the compressor12 and the heat exchanger 14, and serves as a first line. Therefrigerant lines 22, 23 and 24 provide fluid communication between theheat exchanger 14 and the heat exchanger 15. The refrigerant line 25provides fluid communication between the heat exchanger 15 and theexpansion valve 16. The refrigerant line 26 provides fluid communicationbetween the expansion valve 16 and the heat exchanger 18, and serves asa third line. The refrigerant line 27 provides fluid communicationbetween the heat exchanger 18 and the compressor 12, and serves as afourth line.

The refrigerant line 21 is a line for flowing refrigerant from thecompressor 12 to the heat exchanger 14. Refrigerant flows through therefrigerant line 21 from the outlet of the compressor 12 toward theinlet of the heat exchanger 14 between the compressor 12 and the heatexchanger 14. The refrigerant lines 22 to 25 are lines for flowingrefrigerant from the heat exchanger 14 to the expansion valve 16.Refrigerant flows through the refrigerant lines 22 to 25 from the outletof the heat exchanger 14 toward the inlet of the expansion valve 16between the heat exchanger 14 and the expansion valve 16.

The refrigerant line 26 is a line for flowing refrigerant from theexpansion valve 16 to the heat exchanger 18. Refrigerant flows throughthe refrigerant line 26 from the outlet of the expansion valve 16 towardthe inlet of the heat exchanger 18 between the expansion valve 16 andthe heat exchanger 18. The refrigerant line 27 is a line for flowingrefrigerant from the heat exchanger 18 to the compressor 12. Refrigerantflows through the refrigerant line 27 from the outlet of the heatexchanger 18 toward the inlet of the compressor 12 between the heatexchanger 18 and the compressor 12.

The vapor compression refrigeration cycle 10 is formed such that thecompressor 12, the heat exchangers 14 and 15, the expansion valve 16 andthe heat exchanger 18 are coupled by the refrigerant lines 21 to 27.Note that refrigerant used in the vapor compression refrigeration cycle10 may be, for example, carbon dioxide, hydrocarbon, such as propane andisobutane, ammonia, water, or the like.

The gas-liquid separator 40 separates refrigerant, flowing out from theheat exchanger 14, into gaseous refrigerant and liquid refrigerant.Refrigerant liquid that is liquid refrigerant and refrigerant steam thatis gaseous refrigerant are stored inside the gas-liquid separator 40.The refrigerant lines 22 and 23 and the refrigerant line 34 are coupledto the gas-liquid separator 40.

Refrigerant is in a wet steam gas-liquid two-phase state, mixedlycontaining saturated liquid and saturated steam, on the outlet side ofthe heat exchanger 14. Refrigerant flowing out from the heat exchanger14 is supplied to the gas-liquid separator 40 through the refrigerantline 22. Refrigerant in a gas-liquid two-phase state, flowing from therefrigerant line 22 into the gas-liquid separator 40, is separated intogas and liquid inside the gas-liquid separator 40. The gas-liquidseparator 40 separates refrigerant, condensed by the heat exchanger 14,into liquid-state refrigerant liquid and gaseous refrigerant steam andtemporarily stores them.

The separated refrigerant liquid flows out to the outside of thegas-liquid separator 40 via the refrigerant line 34. The end portion ofthe refrigerant line 34 arranged in liquid inside the gas-liquidseparator 40 forms an outlet port through which liquid refrigerant flowsout from the gas-liquid separator 40. The separated refrigerant steamflows out to the outside of the gas-liquid separator 40 via therefrigerant line 23. The end portion of the refrigerant line 23 arrangedin gas inside the gas-liquid separator 40 forms an outlet port throughwhich gaseous refrigerant flows out from the gas-liquid separator 40.Gaseous refrigerant steam delivered from the gas-liquid separator 40radiates heat to the surroundings in the heat exchanger 15 that servesas a third heat exchanger to be cooled to thereby condense.

Inside the gas-liquid separator 40, the refrigerant liquid accumulatesat the lower side and the refrigerant steam accumulates at the upperside. The end portion of the refrigerant line 34 that deliversrefrigerant liquid from the gas-liquid separator 40 is coupled to thebottom portion of the gas-liquid separator 40. Only refrigerant liquidis delivered from the bottom side of the gas-liquid separator 40 to theoutside of the gas-liquid separator 40 via the refrigerant line 34. Theend portion of the refrigerant line 23 that delivers refrigerant steamfrom the gas-liquid separator 40 is coupled to the ceiling portion ofthe gas-liquid separator 40. Only refrigerant steam is delivered fromthe ceiling side of the gas-liquid separator 40 to the outside of thegas-liquid separator 40 via the refrigerant line 23. By so doing, thegas-liquid separator 40 is able to reliably separate gaseous refrigerantand liquid refrigerant from each other.

The path through which refrigerant flows from the outlet of the heatexchanger 14 toward the inlet of the expansion valve 16 includes therefrigerant line 22, the refrigerant line 23, the refrigerant line 24and the refrigerant line 25. The refrigerant line 22 is routed from theoutlet side of the heat exchanger 14 to the gas-liquid separator 40. Therefrigerant line 23 flows out refrigerant steam from the gas-liquidseparator 40, and passes through a flow regulating valve 28 (describedlater). The refrigerant line 24 is coupled to the inlet side of the heatexchanger 15. The refrigerant line 25 flows refrigerant from the outletside of the heat exchanger 15 to the expansion valve 16.

The path of refrigerant that flows between the heat exchanger 14 and theheat exchanger 15 includes the refrigerant line 34 and a refrigerantline 36. The refrigerant line 34 provides fluid communication betweenthe gas-liquid separator 40 and the cooling device 30. The refrigerantline 36 serves as a second line, and provides fluid communicationbetween the cooling device 30 and the refrigerant line 24. Refrigerantliquid flows from the gas-liquid separator 40 to the cooling device 30via the refrigerant line 34. Refrigerant passing through the coolingdevice 30 returns to the refrigerant line 24 via the refrigerant line36. The cooling device 30 is provided on the path of refrigerant flowingfrom the heat exchanger 14 toward the heat exchanger 15.

Point D shown in FIG. 1 indicates a coupling point among the refrigerantline 23, the refrigerant line 24 and the refrigerant line 36. That is,point D indicates the downstream-side (side closer to the heat exchanger15) end portion of the refrigerant line 23, the upstream-side (sidecloser to the heat exchanger 14) end portion of the refrigerant line 24and the downstream-side end portion of the refrigerant line 36. Therefrigerant line 23 forms part of the path routed from the gas-liquidseparator 40 to point D within the path of refrigerant flowing from thegas-liquid separator 40 toward the expansion valve 16.

The cooling system 1 further includes a path of refrigerant arranged inparallel with the refrigerant line 23. The cooling device 30 is providedin that path of refrigerant. The cooling device 30 includes a hybridvehicle (HV) device 31 and a cooling passage 32. The HV device 31 is anelectrical device mounted on the vehicle. The cooling passage 32 is aline through which refrigerant flows. The HV device 31 is an example ofa heat generating source. One end portion of the cooling passage 32 isconnected to the refrigerant line 34. The other end portion of thecooling passage 32 is connected to the refrigerant line 36.

The path of refrigerant, connected in parallel with the refrigerant line23 between the gas-liquid separator 40 and point D shown in FIG. 1,includes the refrigerant line 34 on the upstream side (side closer tothe gas-liquid separator 40) of the cooling device 30, the coolingpassage 32 included in the cooling device 30, and the refrigerant line36 on the downstream side (side closer to the heat exchanger 15) of thecooling device 30. The refrigerant line 34 is a line for flowing liquidrefrigerant from the gas-liquid separator 40 to the cooling device 30.The refrigerant line 36 is a line for flowing refrigerant from thecooling device 30 to point D. Point D is a branching portion between therefrigerant lines 23 and 24 and the refrigerant line 36.

Refrigerant liquid flowing out from the gas-liquid separator 40 flowstoward the cooling device 30 via the refrigerant line 34. Refrigerantthat flows to the cooling device 30 and that flows via the coolingpassage 32 takes heat from the HV device 31 that serves as the heatgenerating source to cool the HV device 31. The cooling device 30 usesliquid refrigerant separated in the gas-liquid separator 40 to cool theHV device 31. Refrigerant flowing through the cooling passage 32exchanges heat with the HV device 31 in the cooling device 30 to coolthe HV device 31, and the refrigerant is heated. Refrigerant furtherflows from the cooling device 30 toward point D via the refrigerant line36, and reaches the heat exchanger 15 via the refrigerant line 24.

The cooling device 30 is configured to be able to exchange heat betweenthe HV device 31 and refrigerant in the cooling passage 32. In thepresent embodiment, the cooling device 30, for example, has the coolingpassage 32 that is formed such that the outer peripheral surface of thecooling passage 32 is in direct contact with the casing of the HV device31. The cooling passage 32 has a portion adjacent to the casing of theHV device 31. At that portion, heat is exchangeable between refrigerant,flowing through the cooling passage 32, and the HV device 31.

The HV device 31 is directly connected to the outer peripheral surfaceof the cooling passage 32 that forms part of the path of refrigerant,routed from the heat exchanger 14 to the heat exchanger 15 in the vaporcompression refrigeration cycle 10, and is cooled. The HV device 31 isarranged on the outside of the cooling passage 32, so the HV device 31does not interfere with flow of refrigerant flowing inside the coolingpassage 32. Therefore, the pressure loss of the vapor compressionrefrigeration cycle 10 does not increase, so the HV device 31 may becooled without increasing the power of the compressor 12.

Alternatively, the cooling device 30 may include a selected known heatpipe that is interposed between the HV device 31 and the cooling passage32. In this case, the HV device 31 is connected to the outer peripheralsurface of the cooling passage 32 via the heat pipe, and heat istransferred from the HV device 31 to the cooling passage 32 via the heatpipe to thereby cool the HV device 31. The HV device 31 serves as aheating portion for heating the heat pipe, and the cooling passage 32serves as a cooling device for cooling the heat pipe to thereby increasethe heat-transfer efficiency between the cooling passage 32 and the HVdevice 31, so the cooling efficiency of the HV device 31 may beimproved. For example, a Wick heat pipe may be used.

Heat may be reliably transferred from the HV device 31 to the coolingpassage 32 by the heat pipe, so there may be a distance between the HVdevice 31 and the cooling passage 32, and complex arrangement of thecooling passage 32 is not required to bring the cooling passage 32 intocontact with the HV device 31. As a result, it is possible to improvethe flexibility of arrangement of the HV device 31.

The HV device 31 includes an electrical device that exchanges electricpower to generate heat. The electrical device includes at least any oneof, for example, an inverter used to convert direct-current power toalternating-current power, a motor generator that is a rotatingelectrical machine, a battery that is an electrical storage device, aconverter that is used to step up the voltage of the battery and a DC/DCconverter that is used to step down the voltage of the battery. Thebattery is a secondary battery, such as a lithium ion battery and anickel metal hydride battery. A capacitor may be used instead of thebattery.

The heat exchanger 18 is arranged inside a duct 90 through which airflows. The heat exchanger 18 exchanges heat between refrigerant andair-conditioning air flowing through the duct 90 to adjust thetemperature of air-conditioning air. The duct 90 has a duct inlet 91 anda duct outlet 92. The duct inlet 91 is an inlet through whichair-conditioning air flows into the duct 90. The duct outlet 92 is anoutlet through which air-conditioning air flows out from the duct 90. Afan 93 is arranged near the duct inlet 91 inside the duct 90.

As the fan 93 is driven, air flows through the duct 90. As the fan 93operates, air-conditioning air flows into the duct 90 via the duct inlet91. Air flowing into the duct 90 may be outside air or may be air in thecabin of the vehicle. The arrow 95 in FIG. 1 indicates flow ofair-conditioning air that flows via the heat exchanger 18 and exchangesheat with refrigerant in the vapor compression refrigeration cycle 10.During cooling operation, air-conditioning air is cooled in the heatexchanger 18, and refrigerant receives heat transferred fromair-conditioning air to be heated. The arrow 96 indicates flow ofair-conditioning air that is adjusted in temperature by the heatexchanger 18 and that flows out from the duct 90 via the duct outlet 92.

Refrigerant passes through a refrigerant circulation path that is formedby sequentially connecting the compressor 12, the heat exchangers 14 and15, the expansion valve 16 and the heat exchanger 18 by the refrigerantlines 21 to 27 to circulate in the vapor compression refrigeration cycle10. Refrigerant flows in the vapor compression refrigeration cycle 10 soas to sequentially pass through points A, B, C, D, E and F shown in FIG.1, and refrigerant circulates among the compressor 12, the heatexchangers 14 and 15, the expansion valve 16 and the heat exchanger 18.

FIG. 2 is a Mollier chart that shows the state of refrigerant in thevapor compression refrigeration cycle 10. In FIG. 2, the abscissa axisrepresents the specific enthalpy (unit: kJ/kg) of refrigerant, and theordinate axis represents the absolute pressure (unit: MPa) ofrefrigerant. The curve in the chart is the saturation vapor line andsaturation liquid line of refrigerant. FIG. 2 shows the thermodynamicstate of refrigerant at points (that is, points A, B, C, D, E and F) inthe vapor compression refrigeration cycle 10 when refrigerant heat flowsfrom the refrigerant line 22 at the outlet of the exchanger 14 into therefrigerant line 34 via the gas-liquid separator 40, cools the HV device31 and returns from the refrigerant line 36 to the refrigerant line 24at the inlet of the heat exchanger 15 via point D.

As shown in FIG. 2, refrigerant (point A) in a superheated steam state,introduced into the compressor 12, is adiabatically compressed in thecompressor 12 along a constant specific entropy line. As refrigerant iscompressed, the refrigerant increases in pressure and temperature intohigh-temperature and high-pressure superheated steam having a highdegree of superheat (point B), and then the refrigerant flows to theheat exchanger 14. Gaseous refrigerant discharged from the compressor 12releases heat to the surroundings to be cooled in the heat exchanger 14to thereby condense (liquefy). Due to heat exchange in the heatexchanger 14, the temperature of refrigerant decreases, and refrigerantliquefies. High-pressure refrigerant steam in the heat exchanger 14becomes dry saturated steam from superheated steam with a constantpressure in the heat exchanger 14, and releases latent heat ofcondensation to gradually liquefy into wet steam in a gas-liquid mixingstate. Condensed refrigerant within refrigerant in a gas-liquidtwo-phase state is in the state of saturated liquid (point C).

Refrigerant is separated in the gas-liquid separator 40 into gaseousrefrigerant and liquid refrigerant. Refrigerant liquid in a liquid phasewithin refrigerant separated into gas and liquid flows from thegas-liquid separator 40 to the cooling passage 32 of the cooling device30 via the refrigerant line 34 to cool the HV device 31. In the coolingdevice 30, heat is released to liquid refrigerant in a saturated liquidstate, which is condensed as it passes through the heat exchanger 14, tothereby cool the HV device 31. Refrigerant is heated by exchanging heatwith the HV device 31, and the dryness of the refrigerant increases.Refrigerant receives latent heat from the HV device 31 to partiallyvaporize into wet steam that mixedly contains saturated liquid andsaturated steam (point D).

After that, refrigerant flows into the heat exchanger 15. Wet steam ofrefrigerant exchanges heat with outside air in the heat exchanger 15 tobe cooled to thereby condense again, becomes saturated liquid as theentire refrigerant condenses, and further releases sensible heat tobecome supercooled liquid (point E). After that, refrigerant flows intothe expansion valve 16 via the refrigerant line 25. In the expansionvalve 16, refrigerant in a supercooled liquid state isthrottle-expanded, and the refrigerant decreases in temperature andpressure with the specific enthalpy unchanged to become low-temperatureand low-pressure wet steam in a gas-liquid mixing state (point F).

Refrigerant in a wet steam state from the expansion valve 16 flows intothe heat exchanger 18 via the refrigerant line 26. Refrigerant in a wetsteam state flows into the tubes of the heat exchanger 18. Whenrefrigerant flows through the tubes of the heat exchanger 18, therefrigerant absorbs heat of air in the cabin of the vehicle as latentheat of vaporization via the fins to evaporate with a constant pressure.As the entire refrigerant becomes dry saturated steam, the refrigerantsteam further increases in temperature by sensible heat to becomesuperheated steam (point A). After that, refrigerant is introduced intothe compressor 12 via the refrigerant line 27. The compressor 12compresses refrigerant flowing from the heat exchanger 18.

Refrigerant continuously repeats changes among the compressed state, thecondensed state, the throttle-expanded state and the evaporated state inaccordance with the above described cycle. Note that, in the abovedescription of the vapor compression refrigeration cycle, a theoreticalrefrigeration cycle is described; however, in the actual vaporcompression refrigeration cycle 10, it is, of course, necessary toconsider a loss in the compressor 12, a pressure loss of refrigerant anda heat loss.

During operation of the vapor compression refrigeration cycle 10,refrigerant absorbs heat of vaporization from air in the cabin of thevehicle at the time when the refrigerant evaporates in the heatexchanger 18 that serves as an evaporator to thereby cool the cabin. Inaddition, high-pressure liquid refrigerant flowing out from the heatexchanger 14 and separated by the gas-liquid separator 40 into gas andliquid flows to the cooling device 30 and exchanges heat with the HVdevice 31 to thereby cool the HV device 31. The cooling system 1 coolsthe HV device 31, which is the heat generating source mounted on thevehicle, by utilizing the vapor compression refrigeration cycle 10 forair-conditioning the cabin of the vehicle. Note that the temperaturerequired to cool the HV device 31 is desirably at least lower than theupper limit of a target temperature range of the HV device 31.

The vapor compression refrigeration cycle 10 that is provided in orderto cool a cooled portion in the heat exchanger 18 is utilized to coolthe HV device 31, so it, is not necessary to provide a device, such asan exclusive water circulation pump and a cooling fan, in order to coolthe HV device 31. Therefore, components required for the cooling system1 to cool the HV device 31 may be reduced to make it possible tosimplify the system configuration, so the manufacturing cost of thecooling system 1 may be reduced. In addition, it is not necessary tooperate a power source, such as a pump and a cooling fan, in order tocool the HV device 31, and power consumption for operating the powersource is not required. Thus, it is possible to reduce power consumptionfor cooling the HV device 31.

In the heat exchanger 14, refrigerant just needs to be cooled into a wetsteam state. Refrigerant in a gas-liquid mixing state is separated bythe gas-liquid separator 40, and only refrigerant liquid in a saturatedliquid state is supplied to the cooling device 30. Refrigerant in a wetsteam state, which receives latent heat of vaporization from the HVdevice 31 to be partially vaporized, is cooled again in the heatexchanger 15. Refrigerant changes in state at a constant temperatureuntil the refrigerant in a wet steam state completely condenses intosaturated liquid. The heat exchanger 15 further supercools liquidrefrigerant to a degree of supercooling required to cool the cabin ofthe vehicle. A degree of supercooling of refrigerant does not need to beexcessively increased, so the capacity of each of the heat exchangers 14and 15 may be reduced. Thus, the cooling performance for cooling thecabin may be ensured, and the size of each of the heat exchangers 14 and15 may be reduced; so it is possible to obtain the cooling system 1 thatis reduced in size and that is advantageous in installation on thevehicle.

The refrigerant line 23 that forms part of the path of refrigerant fromthe outlet of the heat exchanger 14 toward the inlet of the expansionvalve 16 is provided between the heat exchanger 14 and the heatexchanger 15. The refrigerant line 23 that does not pass through thecooling device 30 and the refrigerant lines 34 and 36 and coolingpassage 32 that form the path of refrigerant passing through the coolingdevice 30 to cool the HV device 31 are provided in parallel with eachother as the paths through which refrigerant flowing from the gas-liquidseparator 40 toward the expansion valve 16. The cooling system forcooling the HV device 31, including the refrigerant lines 34 and 36, isconnected in parallel with the refrigerant line 23. Therefore, only partof refrigerant flowing out from the heat exchanger 14 flows to thecooling device 30. Refrigerant in an amount required to cool the HVdevice 31 is caused to flow to the cooling device 30, and the HV device31 is appropriately cooled. Thus, it is possible to prevent excessivecooling of the HV device 31.

The path of refrigerant that directly flows from the heat exchanger 14to the heat exchanger 15 and the path of refrigerant that flows from theheat exchanger 14 to the heat exchanger 15 via the cooling device 30 areprovided in parallel with each other, and only part of refrigerant iscaused to flow to the refrigerant lines 34 and 36. By so doing, it ispossible to reduce the pressure loss at the time when refrigerant flowsthrough the cooling system for cooling the HV device 31. Not the entirerefrigerant flows to the cooling device 30. Therefore, it is possible toreduce the pressure loss associated with flow of refrigerant via thecooling device 30, and, accordingly, it is possible to reduce powerconsumption required to operate the compressor 12 for circulatingrefrigerant.

When low-temperature and low-pressure refrigerant after passing throughthe expansion valve 16 is used to cool the HV device 31, the coolingperformance of air in the cabin in the heat exchanger 18 reduces and thecooling performance for cooling the cabin decreases In contrast to this,in the cooling system 1 according to the present embodiment, in thevapor compression refrigeration cycle 10, high-pressure refrigerantdischarged from the compressor 12 is condensed by both the heatexchanger 14 that serves as a first condenser and the heat exchanger 15that serves as a second condenser. The two-stage heat exchangers 14 and15 are arranged between the compressor 12 and the expansion valve 16,and the cooling device 30 for cooling the HV device 31 is providedbetween the heat exchanger 14 and the heat exchanger 15. The heatexchanger 15 is provided on the path of refrigerant flowing from thecooling device 30 toward the expansion valve 16.

By sufficiently cooling refrigerant, which receives latent heat ofvaporization from the HV device 31 to be heated, in the heat exchanger15, the refrigerant has a temperature and a pressure that are originallyrequired to cool the cabin of the vehicle at the outlet of the expansionvalve 16. Therefore, it is possible to sufficiently increase the amountof heat externally received when refrigerant evaporates in the heatexchanger 18. In this way, by setting the heat radiation performance forthe heat exchanger 15 so as to be able to sufficiently cool refrigerant,the HV device 31 may be cooled without any influence on the coolingperformance for cooling the cabin. Thus, both the cooling performancefor cooling the HV device 31 and the cooling performance for cooling thecabin may be reliably ensured.

When refrigerant flowing from the heat exchanger 14 to the coolingdevice 30 cools the HV device 31, the refrigerant receives heat from theHV device 31 to be heated. As refrigerant is heated to a saturated steamtemperature or above and the entire amount of the refrigerant vaporizesin the cooling device 30, the amount of heat exchanged between therefrigerant and the HV device 31 reduces, and the HV device 31 cannot beefficiently cooled, and, in addition, pressure loss at the time when therefrigerant flows in the line increases. Therefore, it is desirable tosufficiently cool refrigerant in the heat exchanger 14 such that theentire amount of refrigerant does not vaporize after cooling the HVdevice 31.

Specifically, the state of refrigerant at the outlet of the heatexchanger 14 is brought close to saturated liquid, and, typically,refrigerant is placed in a state on the saturated liquid line at theoutlet of the heat exchanger 14. Because the heat exchanger 14 iscapable of sufficiently cooling refrigerant in this way, the heatradiation performance of the heat exchanger 14 for causing refrigerantto release heat is higher than the heat radiation performance of theheat exchanger 15. By sufficiently cooling refrigerant in the heatexchanger 14 having relatively high heat radiation performance,refrigerant that has received heat from the HV device 31 may bemaintained in a wet steam state, and a reduction in the amount of heatexchanged between refrigerant and the HV device 31 may be avoided, so itis possible to sufficiently cool the HV device 31. Refrigerant in a wetsteam state after cooling the HV device 31 is efficiently cooled againin the heat exchanger 15, and is cooled into a supercooled liquid statebelow a saturated temperature. Thus, it is possible to provide thecooling system 1 that ensures both the cooling performance for coolingthe cabin and the cooling performance for cooing the HV device 31.

Refrigerant in a gas-liquid two-phase state at the outlet of the heatexchanger 14 is separated into gas and liquid in the gas-liquidseparator 40. Gaseous refrigerant separated in the gas-liquid separator40 flows via the refrigerant lines 23 and 24 and is directly supplied tothe heat exchanger 15. Liquid refrigerant separated in the gas-liquidseparator 40 flows via the refrigerant line 34 and is supplied to thecooling device 30 to cool the HV device 31. The liquid refrigerant isrefrigerant in a just saturated liquid state. By taking only liquidrefrigerant from the gas-liquid separator 40 and flowing the liquidrefrigerant to the cooling device 30, the performance of the heatexchanger 14 may be fully utilized to cool the HV device 31, so it ispossible to provide the cooling system 1 having improved coolingperformance for cooling the HV device 31.

Refrigerant in a saturated liquid state at the outlet of the gas-liquidseparator 40 is introduced into the cooling passage 32 that cools the HVdevice 31 to thereby make it possible to minimize gaseous refrigerantwithin refrigerant that flows in the cooling system for cooling the HVdevice 31, including the refrigerant lines 34 and 36 and the coolingpassage 32. Therefore, it is possible to suppress an increase inpressure loss due to an increase in flow rate of refrigerant steamflowing in the cooling system for cooling the HV device 31, and thepower consumption of the compressor 12 for flowing refrigerant may bereduced, so it is possible to avoid deterioration of the performance ofthe vapor compression refrigeration cycle 10.

Refrigerant liquid in a saturated liquid state is stored inside thegas-liquid separator 40. The gas-liquid separator 40 functions as areservoir that temporarily stores refrigerant liquid that is liquidrefrigerant inside. When refrigerant liquid in a predetermined amount isstored in the gas-liquid separator 40, the flow rate of refrigerantflowing from the gas-liquid separator 40 to the cooling device 30 may bemaintained at the time of fluctuations in load. Because the gas-liquidseparator 40 has the function of storing liquid, serves as a bufferagainst load fluctuations and is able to absorb load fluctuations, thecooling performance for cooling the HV device 31 may be stabilized.

Referring back to FIG. 1, the cooling system 1 includes a flowregulating valve 28. The flow regulating valve 28 is arranged in therefrigerant line 23, which forms one of the parallel connected paths, onthe path of refrigerant from the heat exchanger 14 toward the expansionvalve 16. The flow regulating valve 28 changes its valve opening degreeto increase or reduce the pressure loss of refrigerant flowing in therefrigerant line 23 to thereby selectively adjust the flow rate ofrefrigerant flowing in the refrigerant line 23 and the flow rate ofrefrigerant flowing in the cooling system for cooing the HV device 31,including the cooling passage 32.

For example, as the flow regulating valve 28 is fully closed to set thevalve opening degree at 0%, the entire amount of refrigerant from theheat exchanger 14 flows into the refrigerant line 34 via the gas-liquidseparator 40. When the valve opening degree of the flow regulating valve28 is increased, the flow rate of refrigerant that flows directly to theheat exchanger 15 via the refrigerant line 23 increases and the flowrate of refrigerant that flows to the cooling passage 32 via therefrigerant line 34 to cool the HV device 31 reduces within refrigerantthat flows from the heat exchanger 14 to the refrigerant line 22. Whenthe valve opening degree of the flow regulating valve 28 is reduced, theflow rate of refrigerant that directly flows to the heat exchanger 15via the refrigerant line 23 reduces and the flow rate of refrigerantthat flows via the cooling passage 32 to cool the HV device 31 increaseswithin refrigerant that flows from the heat exchanger 14 to therefrigerant line 22.

As the valve opening degree of the flow regulating valve 28 isincreased, the flow rate of refrigerant that cools the HV device 31reduces, so cooling performance for cooling the HV device 31 decreases.As the valve opening degree of the flow regulating valve 28 reduces, theflow rate of refrigerant that cools the HV device 31 increases, socooling performance for cooling the HV device 31 improves. The flowregulating valve 28 is used to make it possible to optimally adjust theamount of refrigerant flowing to the HV device 31, so it is possible toreliably prevent excessive cooling of the HV device 31, and, inaddition, it is possible to reliably reduce pressure loss associatedwith flow of refrigerant in the cooling system for cooling the HV device31 and the power consumption of the compressor 12 for circulatingrefrigerant.

The cooling system 1 further includes a communication line 51. Thecommunication line 51 provides fluid communication between therefrigerant line 21, through which refrigerant flows between thecompressor 12 and the heat exchanger 14, and the refrigerant line 36 onthe downstream side of the cooling device 30 between the refrigerantlines 34 and 36 that flow refrigerant through the cooling device 30. Aselector valve 52 is provided in the refrigerant line 36 and thecommunication line 51. The selector valve 52 switches the state of fluidcommunication between the communication line 51 and the refrigerantlines 21 and 36. The selector valve 52 switches between the open stateand the closed state to thereby allow or interrupt flow of refrigerantvia the communication line 51. The refrigerant line 36 is divided into arefrigerant line 36 a on the upstream side of a branching portion fromthe communication line 51 and a refrigerant line 36 b on the downstreamside of the branching portion from the communication line 51.

By switching the path of refrigerant using the selector valve 52,refrigerant after cooling the HV device 31 may be caused to flow to anyselected one of the paths, that is, to the heat exchanger 15 via therefrigerant lines 36 b and 24 or to the heat exchanger 14 via thecommunication line 51 and the refrigerant line 21.

More specifically, two valves 57 and 58 are provided as the selectorvalve 52. During cooling operation of the vapor compressionrefrigeration cycle 10, the valve 57 is fully open (valve opening degree100%) and the valve 58 is fully closed (valve opening degree 0%), andthe valve opening degree of the flow regulating valve 28 is adjustedsuch that a sufficient amount of refrigerant flows through the coolingdevice 30. By so doing, refrigerant flowing through the cooling passage36 a after cooling the HV device 31 may be reliably caused to flow tothe heat exchanger 15 via the refrigerant line 36 b. On the other hand,during a stop of the vapor compression refrigeration cycle 10, the valve58 is fully open and the valve 57 is fully closed, and, furthermore, theflow regulating valve 28 is fully closed. By so doing, refrigerantflowing through the refrigerant line 36 a after cooling the HV device 31may be caused to flow to the heat exchanger 14 via the communicationline 51 to make it possible to form an annular path that causesrefrigerant to circulate between the cooling device 30 and the heatexchanger 14.

FIG. 3 is a schematic view that shows flow of refrigerant that cools theHV device 31 during operation of the vapor compression refrigerationcycle 10. FIG. 4 is a schematic view that shows flow of refrigerant thatcools the HV device 31 during a stop of the vapor compressionrefrigeration cycle 10. FIG. 3 shows flow of refrigerant when the vaporcompression refrigeration cycle 10 is operated, that is, when thecompressor 12 is operated to flow refrigerant through the whole of thevapor compression refrigeration cycle 10. On the other hand, FIG. 4shows flow of refrigerant when the vapor compression refrigeration cycle10 is stopped, that is, when the compressor 12 is stopped to circulaterefrigerant via the annular path that connects the cooling device 30 tothe heat exchanger 14.

As shown in FIG. 3, during “air-conditioner operation mode” in which thecompressor 12 is driven and the vapor compression refrigeration cycle 10is operated, the flow regulating valve 28 is adjusted in valve openingdegree such that a sufficient amount of refrigerant flows through thecooling device 30. The selector valve 52 is operated so as to flowrefrigerant from the cooling device 30 to the expansion valve 16 via theheat exchanger 15. That is, as the valve 57 is fully open and the valve58 is fully closed, the path of refrigerant that causes refrigerant toflow through the whole of the cooling system 1 is selected. Therefore,the cooling performance of the vapor compression refrigeration cycle 10may be ensured, and the HV device 31 may be efficiently cooled.

As shown in FIG. 4, during “heat pipe operation mode” in which thecompressor 12 is stopped and the vapor compression refrigeration cycle10 is stopped, the selector valve 52 is operated so as to circulaterefrigerant from the cooling device 30 to the heat exchanger 14. Thatis, as the valve 57 is fully closed, the valve 58 is fully open and theflow regulating valve 28 is fully closed, refrigerant does not flow tothe refrigerant line 36 b but flows via the communication line 51. By sodoing, a closed annular path is formed. The closed annular path isrouted from the heat exchanger 14 to the cooling device 30 via therefrigerant line 22 and the refrigerant line 34 sequentially, furtherpasses through the refrigerant line 36 a, the communication line 51 andthe refrigerant line 21 sequentially and returns to the heat exchanger14.

Refrigerant may be circulated between the heat exchanger 14 and thecooling device 30 via the annular path without operating the compressor12. When refrigerant cools the HV device 31, the refrigerant receiveslatent heat of vaporization from the HV device 31 to evaporate.Refrigerant steam vaporized by exchanging heat with the HV device 31flows to the heat exchanger 14 via the refrigerant line 36 a, thecommunication line 51 and the refrigerant line 21 sequentially. In theheat exchanger 14, refrigerant steam is cooled to condense by runningwind of the vehicle or draft from an engine cooling radiator fan.Refrigerant liquid liquefied in the heat exchanger 14 returns to thecooling device 30 via the refrigerant lines 22 and 34.

In this way, a heat pipe in which the HV device 31 serves as a heatingportion and the heat exchanger 14 serves as a cooling device is formedby the annular path that passes through the cooling device 30 and theheat exchanger 14. Thus, when the vapor compression refrigeration cycle10 is stopped, that is, when a cooler for the vehicle is stopped aswell, the HV device 31 may be reliably cooled without the necessity ofstart-up of the compressor 12. Because the compressor 12 is not requiredto constantly operate in order to cool the HV device 31, the powerconsumption of the compressor 12 is reduced to thereby make it possibleto improve the fuel economy of the vehicle and, in addition, to extendthe life of the compressor 12, so it is possible to improve thereliability of the compressor 12.

FIG. 3 and FIG. 4 show a ground 60. The cooling device 30 is arrangedbelow the heat exchanger 14 in the vertical direction perpendicular tothe ground 60. In the annular path that circulates refrigerant betweenthe heat exchanger 14 and the cooling device 30, the cooling device 30is arranged below, and the heat exchanger 14 is arranged above. The heatexchanger 14 is arranged at the level higher than the cooling device 30.

In this case, refrigerant steam heated and vaporized in the coolingdevice 30 goes up in the annular path, reaches the heat exchanger 14, iscooled in the heat exchanger 14, condenses into liquid refrigerant, goesdown in the annular path by the action of gravity and returns to thecooling device 30. That is, a thermo-siphon heat pipe is formed of thecooling device 30, the heat exchanger 14 and the refrigerant paths thatconnect them. Because the heat transfer efficiency from the HV device 31to the heat exchanger 14 may be improved by forming the heat pipe, whenthe vapor compression refrigeration cycle 10 is stopped as well, the HVdevice 31 may be further efficiently cooled without additional power.

The selector valve 52 that switches the state of fluid communicationbetween the communication line 51 and the refrigerant lines 21 and 36may be the above described pair of valves 57 and 58 or may be athree-way valve that is arranged at the branching portion between therefrigerant line 36 and the communication line 51. In any cases, duringboth operation and stop of the vapor compression refrigeration cycle 10,the HV device 31 may be efficiently cooled. The valves 57 and 58 justneed to have a simple structure so as to be able to open or close therefrigerant line, so the valves 57 and 58 are not expensive, and the twovalves 57 and 58 are used to make it possible to provide the furtherlow-cost cooling system 1. On the other hand, it is presumable that aspace required to arrange the three-way valve is smaller than a spacerequired to arrange the two valves 57 and 58, and the three-way valve isused to make it possible to provide the cooling system 1 having afurther reduced size and excellent vehicle mountability.

The cooling system 1 further includes a check valve 54. The check valve54 is arranged in the refrigerant line 21 between the compressor 12 andthe heat exchanger 14 on the side closer to the compressor 12 than theconnection portion between the refrigerant line 21 and the communicationline 51. The check valve 54 allows flow of refrigerant from thecompressor 12 toward the heat exchanger 14 and prohibits, flow ofrefrigerant in the opposite direction. By so doing, during the heat pipeoperation mode shown in FIG. 4, a closed loop path of refrigerant forcirculating refrigerant between the heat exchanger 14 and the coolingdevice 30 may be reliably formed.

When no check valve 54 is provided, refrigerant may flow from thecommunication line 51 to the refrigerant line 21 adjacent to thecompressor 12. By providing the check valve 54, it is possible toreliably prohibit flow of refrigerant from the communication line 51toward the side adjacent to the compressor 12, so it is possible toprevent a decrease in the cooling performance for cooling the HV device31 during a stop of the vapor compression refrigeration cycle 10, usingthe heat pipe that forms the annular refrigerant path. Thus, when thecooler for the cabin of the vehicle is stopped as well, it is possibleto efficiently cool the HV device 31.

In addition, when the amount of refrigerant in the closed loop path ofrefrigerant is insufficient during a stop of the vapor compressionrefrigeration cycle 10, the compressor 12 is operated only in a shortperiod of time to thereby make it possible to supply refrigerant to theclosed loop path via the check valve 54. By so doing, the amount ofrefrigerant in the closed loop may be increased to thereby increase theamount of heat exchanged in the heat pipe. Thus, the amount ofrefrigerant in the heat pipe may be ensured, so it is possible to avoidinsufficient cooling of the HV device 31 because of an insufficientamount of refrigerant.

Hereinafter, the detailed structure of the cooling device 30 will bedescribed. FIG. 5 is a partially cross-sectional view of the coolingdevice 30. The HV device 31 that serves as the heat generating sourceincludes a plurality of HV devices 31 a to 31 d. The HV devices 31 a to31 d are mounted on a substrate 70. The HV devices 31 a to 31 d are, forexample, insulated gate bipolar transistors (IGBTs) included in aninverter and/or a converter. The HV devices 31 (31 a to 31 d) are inthermal contact with the outer face 69 of the bottom portion 65 of thecooling passage 32 via the substrate 70. As described above, thesubstrate 70 may be directly in contact with the outer face 69 or a heatpipe may be interposed between the substrate 70 and the outer face 69.

The cooling passage 32 included in the cooling device 30 has a tankshape. Refrigerant flows through the internal space of the coolingpassage 32. The Cooling passage 32 has an inlet end portion 61 and anoutlet end portion 63. The inlet end portion 61 is an end portion towhich the refrigerant line 34 is coupled. The outlet end portion 63 isan end portion to which the refrigerant line 36 is coupled. The inletend portion 61 shown at the left side in FIG. 5 has a through hole 62.Refrigerant flowing through the refrigerant line 34 flows into thecooling passage 32 via the through hole 62. The outlet end portion 63shown at the right side in FIG. 5 has a through hole 64. Refrigerantflows out from the cooling passage 32 via the through hole 64, and flowsto the refrigerant line 36.

The cooling passage 32 also has the bottom portion 65. The bottomportion 65 forms part of the vertically lower side of the coolingpassage 32. Liquid refrigerant flowing inside the cooling passage 32flows along the bottom portion 65 from the inlet end portion 61 towardthe outlet end portion 63. The bottom portion 65 has an inner face 66and the outer face 69. Liquid refrigerant flowing inside the coolingpassage 32 contacts with the inner face 66 of the bottom portion 65. Theinner face 66 is a contact face with which refrigerant liquid contacts.

FIG. 6 is a partially enlarged perspective view of the inner face 66 ofthe bottom portion 65 of the cooling passage 32. As shown in FIG. 6, theinner face 66 is subjected to surface processing to thereby form aplurality of ridges 67 and a plurality of grooves 68. The ridges 67 andthe grooves 68 extend from the inlet end portion 61 of the coolingpassage 32 toward the outlet end portion 63. That is, the ridges 67 andthe grooves 68 extend in the flow direction of refrigerant that flowsinside the cooling passage 32.

Surface processing to which the inner face 66 is subjected in order toform the ridges 67 and the grooves 68 may be any known processing. Forexample, small grooves are formed on the inner face 66 to partiallyrecess the inner face 66 to thereby form the ridges 67 and the grooves68 or small fins are assembled to the inner face 66 to partiallyprotrude the inner face 66 to thereby form the ridges 67 and the grooves68. In addition, the shape of the inner face 66 is not limited to theshape having the ridges 67 and the grooves 68. For example, a pluralityof pores may be formed in the inner face 66 to form the bottom portion65 in a porous shape or a mesh member may be assembled to the inner face66.

The inner face 66 is subjected to processing to thereby form acapillarity generating portion by which liquid refrigerant is movablefrom the lower side to the upper side because of capillarity. In thecase of the inner face 66 configured as shown in FIG. 6, the grooves 68function as the capillarity generating portion. That is, when thecooling passage 32 is inclined such that one of the inlet end portion 61and the outlet end portion 63 is located on the upper side and the otherone is located on the lower side, refrigerant liquid is able to risefrom the lower one of the inlet end portion 61 and the outlet endportion 63 toward the upper one through the grooves 68.

FIG. 7 is a schematic view that shows a vehicle 100 that is running on aflat road. FIG. 8 is a cross-sectional view that shows the state ofrefrigerant liquid 80 inside the cooling passage 32 while the vehicle100 is running on the flat, road. When the vehicle 100 is running on theflat ground 60 shown in FIG. 7, the cooling device 30 is maintainedparallel to the ground 60. Therefore, as shown in FIG. 8, the bottomportion 65 of the cooling passage 32 is arranged substantiallyhorizontally, and the liquid surface of the refrigerant liquid 80 isalso substantially horizontal. As described with reference to FIG. 1 andFIG. 2, liquid refrigerant flows from the inlet end portion 61 into thecooling passage 32, and the refrigerant liquid 80 is stored inside thecooling passage 32.

The refrigerant liquid 80 is in contact with the entire bottom portion65 of the cooling passage 32, so the plurality of HV devices 31 a to 31d are uniformly cooled. Refrigerant steam that is generated throughevaporation of the refrigerant liquid 80 as a result of heat exchangebetween refrigerant and the HV device 31 inside the cooling passage 32flows out from the cooling passage 32 via the through hole 64 of theoutlet end portion 63.

FIG. 9 is a schematic view that shows the vehicle 100 that is running onan uphill. FIG. 10 is a cross-sectional view that shows the state of therefrigerant liquid 80 inside the cooling passage 32 while the vehicle100 is running on the uphill. When the ground 60 is inclined withrespect to a horizontal plane and the vehicle 100 is running so as to goup the inclined ground 60 as shown in FIG. 9, the cooling passage 32 isinclined such that the inlet end portion 61 is relatively located on theupper side and the outlet end portion 63 is relatively located on thelower side as shown in FIG. 10. Therefore, the bottom portion 65 of thecooling passage 32 is also inclined such that the side adjacent to theinlet end portion 61 is located at a higher position and the sideadjacent to the outlet end portion 63 is located at a lower position.

In this case, refrigerant that flows into the cooling passage 32 via thethrough hole 62 of the inlet end portion 61 flows from the side adjacentto the inlet end portion 61, located at a relatively high position,toward the side adjacent to the outlet end portion 63, and therefrigerant liquid 80 forms liquid pool at the outlet end portion 63located at a relatively low position. The refrigerant liquid 80continuously flows from the inlet end portion 61 to the outlet endportion 63 to maintain a state where the refrigerant liquid 80 contactswith the entire bottom portion 65 of the cooling passage 32. Therefore,the plurality of HV devices 31 a to 31 d are uniformly cooled.

FIG. 11 is a schematic view that shows the vehicle 100 that is runningon a downhill. FIG. 12 is a cross-sectional view that shows the state ofthe refrigerant liquid 80 inside the cooling passage 32 while thevehicle 100 is running on the downhill. When the ground 60 is inclinedwith respect to a horizontal plane and the vehicle is running so as togo down the inclined ground 60 as shown in FIG. 11, the cooling passage32 is inclined such that the inlet end portion 61 is relatively locatedon the lower side and the outlet end portion 63 is relatively located onthe upper side as shown in FIG. 12. Therefore, the bottom portion 65 ofthe cooling passage 32 is also inclined such that the side adjacent tothe inlet end portion 61 is located at a relatively low position and theside adjacent to the outlet end portion 63 is located at a relativelyhigh position.

In this case, refrigerant flowing into the cooling passage 32 formsliquid pool at the inlet end portion 61 located at a relatively lowposition because of the inclined bottom portion 65. Here, the inner face66 of the bottom portion 65 of the cooling passage 32 according to thepresent embodiment has the plurality of grooves 68 that function as thecapillarity generating portion and that are described with reference toFIG. 6. Therefore, the refrigerant liquid 80 flows through the groovesso as to rise from the side adjacent to the inlet end portion 61 towardthe side adjacent to the outlet end portion 63 due to capillarity.

Refrigerant liquid is caused to uniformly reach all the areas in thedirection in which refrigerant liquid flows inside the cooling device 30by utilizing capillarity to thereby maintain a state where therefrigerant liquid 80 contacts with the bottom portion 65 at the outletend portion 63 as well. The amount of the refrigerant liquid 80 thatflows toward the outlet end portion 63 in the grooves 68 usingcapillarity as driving force is small such that the liquid surface doesnot reach the height of the inner face 66. However, due to flow of therefrigerant liquid 80, a state where the refrigerant liquid 80 is incontact with the bottom portion 65 is kept over the entire bottomportion 65. Therefore, the cooling performance for cooling the HV device31 does not fluctuate among positions within the bottom portion 65. Thatis, the HV device 31 a adjacent to the inlet end portion 61 and the HVdevice 31 d adjacent to the outlet end portion 63 are cooled by therefrigerant liquid 80 with the same cooling performance. Thus, theplurality of HV devices 31 a to 31 d may be uniformly cooled.

When the cooling passage 32 is inclined with running of the vehicle 100and then a state (dryout) where the refrigerant liquid 80 partially doesnot contact with the bottom portion 65 of the cooling passage 32 occurs,the cooling performance for cooling any one of the HV devices 31 at thatportion decreases. As a result, there occurs an inconvenience that theplurality of HV devices 31 cannot be uniformly cooled. In contrast tothis, in the cooling system 1 according to the present embodiment, theinner face 66 of the bottom portion 65 of the cooling passage 32 has thecapillarity generating portion. By so doing, even when the vehicle 100is inclined, refrigerant liquid is caused to rise due to capillarity tothereby make it possible to keep a state where the entire bottom portion65 is in contact with the refrigerant liquid 80. Therefore, it ispossible to avoid occurrence of an inconvenience that the HV devices 31are nonuniformly cooled.

Depending on the condition that the cooling device 30 is mounted on thevehicle 100, it is conceivable that the cooling passage 32 may beinclined even while the vehicle 100 is running on a flat road. In such acase as well, the capillarity generating portion is provided to therebymake it possible to cause refrigerant liquid to rise due to capillarityas in the case of the above, so a state where the entire bottom portion65 is in contact with the refrigerant liquid 80 may be kept irrespectiveof the condition that the cooling device 30 is mounted, and it ispossible to ensure the cooling performance for cooling the HV devices31.

During the “air-conditioner operation mode” described with reference toFIG. 3, because the compressor 12 is driven, driving force for flowingrefrigerant inside the cooling passage 32 is large, and dryout is hardto occur. In contrast to this, during the “heat pipe operation mode”described with reference to FIG. 4, a pressure difference that slightlyoccurs between the cooling device 30 and the heat exchanger 14 andliquid refrigerant supplied from the heat exchanger 14 to the coolingdevice 30 due to gravity operate as driving force for flowingrefrigerant into the cooling passage 32. That is, during the “heat pipeoperation mode”, driving force that acts on refrigerant is relativelysmall, and the flow rate of refrigerant is relatively low, so dryouttends to occur.

Therefore, in the case of the cooling system 1 according to the presentembodiment, which includes the communication line 51 to make it possibleto switch between the “air-conditioner operation mode” and the “heatpipe operation mode”, the inner face 66 of the bottom portion 65 insidethe cooling passage 32 particularly desirably has the capillaritygenerating portion. The capillarity generating portion is formed of theabove described grooves 68, or the like, to generate driving force. Byso doing, during the “heat pipe operation mode” in which the flow rateof refrigerant is low as well, it is possible to further reliably supplyrefrigerant in a liquid state to the entire bottom portion 65. Thus,occurrence of dryout may be further suppressed, so the HV devices 31 maybe further uniformly cooled.

Note that, in the above described embodiment, the cooling system 1 thatcools an electrical device mounted on the vehicle is described using theHV device 31 as an example. The electrical device is not limited to theillustrated electrical devices, such as an inverter and a motorgenerator. The electrical device may be any electrical device as long asit generates heat when it is operated. In the case where there are aplurality of electrical devices to be cooled, the plurality ofelectrical devices desirably have a common cooling target temperaturerange. The target temperature range for cooling is an appropriatetemperature range as a temperature environment in which the electricaldevices are operated.

The embodiment of the invention is described above. The embodimentdescribed above should be regarded as only illustrative in every respectand not restrictive The scope of the invention is indicated not by theabove description but by the appended claims, and is intended to includeall modifications within the meaning and scope equivalent to the scopeof the appended claims.

The cooling system according to the aspect of the invention may beparticularly advantageously applied to cooling of an electrical device,such as a motor generator and an inverter, using a vapor compressionrefrigeration cycle for cooling a cabin, in a vehicle, such as a hybridvehicle, a fuel-cell vehicle and an electric vehicle, equipped with theelectrical device.

1. A cooling system configured to cool a heat generating source mountedon a vehicle, comprising: a compressor configured to circulaterefrigerant; a first heat exchanger configured to perform heat exchangebetween the refrigerant and outside air; a decompressor configured todecompress the refrigerant; a second heat exchanger configured toperform heat exchange between the refrigerant and air-conditioning air;and a cooling device configured to be provided on a path of therefrigerant flowing between the first heat exchanger and thedecompressor and configured to use the refrigerant to cool the heatgenerating source, the cooling device including a capillarity generatingportion that causes the refrigerant to rise due to capillarity.
 2. Thecooling system according to claim 1, wherein the capillarity generatingportion is configured to be formed by subjecting an inner face of abottom portion of the cooling device to surface processing.
 3. Thecooling system according to claim 2, wherein the inner face of thebottom portion of the cooling device has a plurality of grooves.
 4. Thecooling system according to claim 1, wherein the capillarity generatingportion extends in a flow direction of the refrigerant flowing throughthe cooling device.
 5. The cooling system according to claim 1, whereinthe heat generating source is in thermal contact with an outer face of abottom portion of the cooling device.
 6. The cooling system according toclaim 5, wherein the heat generating source is directly in contact withthe outer face of the bottom portion of the cooling device or is incontact with the outer face via a heat pipe.
 7. The cooling systemaccording to claim 1, further comprising: a first line through which therefrigerant flows between the compressor and the first heat exchanger; asecond line through which the refrigerant flows between the coolingdevice and the decompressor; and a communication line configured toprovide fluid communication between the first line and the second line.8. The cooling system according to claim 7, further comprising: a thirdline through which the refrigerant flows between the decompressor andthe second heat exchanger; and a fourth line through which therefrigerant flows between the second heat exchanger and the compressor.